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I about to embark on home theater 2. The first one was sold with our previous house. It was very traditional setup with gobs of wires and components. For this iteration I would like to go 100% digital HTPC. Linux greatly preferred.


The first problem I'm encountering is with DVI. How can I tell if a projector (Optoma H76) can be driven at it's native resolution over DVI? Is this a factor of DVI-D vs. DVI-I?


Second, is there a color/quality difference with driving the projector from a PC and playing a DVD vs playing on a DVD player with DVI-out? It was mentioned to me by a dealer that pc DVI out would not provide the same color as DVI out from a DVD player. Was he talking smack?


I had assumed that DVI was relatively straight-forward and purchased a Sharp LC30HV2U to test it out. But as it turns out the darn thing would only accept 480p and 720p over DVI; that made it impossible to achieve a pixel-perfect PC desktop. I hastily returned it. I'd rather not find the same thing out the hard way with a projector which is much harder to return.


thanks
 

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I am interested in the same thing.


As far as I can tell, you should be able to set some options in XF86Config to indicate that the display device accepts DVI. For example, the driver for my Geforce FX 5600 card has an option DFP (digital flat panel), and apparently this needs to be included for DVI. I haven't yet figured out how to set this part up for my projector, so I would really appreciate some help on exactly how to configure XF86config.


Dave
 

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Denon AVR-X4400H, Pioneer HPM-100s, Pro-ject, DT ProMonitor 800s, SVS SB2000, 60" LG 4KTV
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DVI-I is "integrated" analog and digital. DVD-D is digital only. DVI-A is essentially RGBHV. I have used GForce4 MX, which has a DVI-I output, with a DVI-D connection to a LCD panel just fine. You just need to get the proper cable to connect. You can find XFree86Config modelines here for 480p and 720p output. I have successfully used 1280x720p VGA output to a plasma panel.
 

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I have run DVI-D from an NVIDIA FX5200 to my Sharp m20X projector. I do not do this right now because of one major problem. the video card talks to the projector over DVI-D, the projector gives a list of supported resolutions to the video card. The native (And I believe the first resolution returned) is 1024x768. The video card does this great.


However, 1024x768 is not 16:9 that my screen is. After trying about 15 resolutions, the projector appeared to either get a resolution of 1024x768 or 1280x1024 at 60hz regardless of what custom resolutions and modelines I chose. I've been told, but still need to verify, that the nvidia card does internal scaling to the "first/native" resolution reported by a monitor/projector.


I use 1024x576 over a 15 pin d-sub cable (normal vga cable). It works well, and although not digital, it will do great until NVIDIA releases a driver that doesn't do what it's doing, or I buy another card. And no, disabling noDCC and DPMS doesn't have any effect.


As for DVI-D from a pc Vs. a DVD player, a PC uses values 0-256. DVD /consumer electronic eqipment uses something like 14-240. Some displays auto detect which one of these ranges is being sent, others let you pick in a menu, and others use only 1 range. If your monitor/projector/display/whatever uses only 1 range (probably 14-240) then you loose what would be considered shadow detail and bright detail. (Basically any value below 14 is considered 14, and any over 240 is considered 240). To some people this will be important, but my opinion is if you're using a Linux HTPC and wanting to watch a DVD, that's the least of your problems. Try comparing a $50 dvd player to any Linux HTPC and you'll notice very ugly video when panning. Linux doesn't support correct video syncing and motion is nowhere near smooth. And even non-knowledgeable people pick up on it very fast. (To fix this, NVIDIA and other companies need to be hounded to supoort _real_ sync support as done in windows, and not even fake syncing done on matrox cards... And the X server needs to be able to watch syncing, and so do video players such as xine, ogle, and mplayer.


If you want a fun toy, use a Linux HTPC, if you want something that works well but you pay more, use a windows HTPC, if you want the best, use HT equipment.


--Brandon
 

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Hey now, don't take that the wrong way. :) Most HTPC's are a fun toy, (and a fun toy is a hobby to me). I still prefer a fun toy to windows or forking out $20k for a home theater. If a HTPC isn't a fun toy, it's being used for "research" (aka toying around with). But for those who don't see a HTPC as a toy (not including telling their wife or kids it isn't a toy) and for those who want to spend money rather than person time building their own Linux HTPC (maybe for a hobby) then to be honest, Linux isn't the best choice _yet_ -- But I have no doubt it will be much better in the future, but it isn't as good as other choices this month. And the reason I think it's not as good as smooth video for DVD and HD playback is greatly lacking. And MythTV isn't as advanced as other applications. But I'm possitive it will be better in a few months. It started after others but it's progressing several magnitudes faster than any other application, and will do so until it's almost feature complete, such as xmms.


--Brandon
 

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I didn't. Sorry. I agree with you completely. Just having fun.


Who wouldn't want a toy and hang out in these forums? It is all about the hacking.
 

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So far the smoothest video I've seen in software playback is from mplayer -autosync 120 (the autosync parameter tells mplayer to try to sync audio to video averaged over a long period of time, rather than every frame). This works very well with constant framerate material, but with stuff that frequently switches between 29.97/24 (for example), there will be a lot of jerkiness for about 120 frames after the transition. I'm sure I've seen better playback from Ogle and/or Xine in the past, but with my current setup (2.4.20 with some performance patches and HZ=1024, and the latest versions of Ogle and Xine, perfect 59.94 refresh rate) both Ogle and Xine are quite jerky. I believe that tvtime has smooth output, though; I wonder why the media player developers can't get it right. Once Xine's tvtime plugin is fixed to support bottom-field-first frames, I think that there may be a big improvement there.
 
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